Many cities are attempting to conserve water by reducing the amount of water used in each toilet flushing. One approach to reducing flush water while still assuring effective removal of toilet debris, is to apply a vacuum to the toilet bowl outlet near the beginning of each flushing, to suck out water and debris from the water closet into a drain pipe. One old patent, No. 380,854 to Boyle, issued Apr. 10, 1888, describes a vacuum assisted toilet which includes a container lying in the tank, with its bottom open to the rest of the tank and its top sealed. A vacuum conduit extends from the top of the tank to the toilet bowl outlet. When a person pulls a chain, he lifts the container to create a vacuum at its top, while simultaneously lifting a flush valve lying under the container. A vacuum created during lifting of the container produces a vacuum in the toilet outlet to assist flushing. The toilet outlet includes upper and lower traps that are always sealed against the passage of air, with the vacuum applied between the traps.
The system described in the Boyle Pat. No. 380,854 has several disadvantages, including the resistance to lifting a wide area tank against the vacuum created during such lifting, and the possibility that his two traps will allow all water from the toilet bowl to be siphoned into the drain. His system would violate present plumbing codes because of the possibility that sewer gas could leak into the environment. A vacuum assisted toilet of simple construction, which used a minimum of moving parts, and only those parts which have become highly reliable during years of refinement, and which complied with building codes against the possibility of sewer gas leakage, would be of considerable value.